CATADIOPTRIC LENS, OPTICAL HEAD, AND OPTICAL RECORDING/REPRODUCING APPARATUS

摘要

A lens which has corrected the coma aberration substantially completely is provided as a catadioptric lens used with advantage in utilizing the evanescent light. The catadioptric lens is a concave non-spherical mirror having a concave refractive surface as a first surface S1, a plane mirror as a second surface S2 and a concave non-spherical mirror arranged coaxially with the concave refractive surface of the first surface S1. The parallel incident light is converged through an aperture in the plane mirror of the second surface S2 on a total reflection plane of the fourth surface S4. The radius of curvature of the first surface S1 and the optical length d from the first surface S1 to the apex of the third surface S3 are set to satisfy the sine condition.